ARM966: remove exports and forward decls

Unneeded exports cause confusion about the module interfaces.
Make most functions static.

The forward decls are just code clutter; remove them, by moving
their references after definitions.  This is another file which
never needed even one internal forward declaration.

Also remove needless arm966e_init_target(), in favor of the
arm9tdmi routine to which it delegates its work.

This saved over 100 bytes of code on x86_32.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>